Watercraft manoeuvring device and a surface watercraft including the manoeuvring device

ABSTRACT

A watercraft manoeuvring device for mounting on a watercraft is disclosed comprising an elongate member having a mounting end and an opposed fin end that is spaced from the mounting end. The device includes a mounting formation on the mounting end for mounting on the watercraft and a fin mounted on the fin end. The fin has a bearing surface for interacting with water and the elongate member is capable of flexing when the fin is subjected to hydrodynamic water forces when travelling through water. The device may be integrally formed from a polymeric material. A watercraft such as a surfboard having the watercraft manoeuvring device is also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a United States National Filing, which claimspriority benefit under 35 U.S.C. § 119(a) of Australian National Patentapplication No. 2020903492 filed Sep. 28, 2020, entitled “A WatercraftManoeuvring Device and A Surface Watercraft Including The ManoeuvringDevice”, which is incorporated herein by reference in its entireties.

TECHNICAL FIELD

This invention relates to a watercraft manoeuvring device and a surfacewatercraft including the manoeuvring device.

This invention relates particularly, but not exclusively, to a surfacewatercraft that is a surfboard, and it will be convenient to hereinafterdescribe this invention with reference to this example application.However, it should be clearly understood that the invention is capableof broader application. For example, it could be applied to wind surfersand also to other surface watercrafts.

BACKGROUND OF THE INVENTION

Surfboards are well known and typically comprise an elongate boardhaving operatively upper and lower surfaces. The lower surface of theboard travels across the surface of the water with one or more finstowards the rear projecting transversely down from the operatively lowersurface.

The Applicant is aware of some developments in the design of the shapeof fins. However, as far as Applicant is aware, in the prior art, thefins have always been directly mounted to the board and have a base thatis attached to the surfboard along a base line. Thus, the base of thefin is fast with the board and while it can bend on the board it cannotbe displaced relative to the board.

Each fin in its downward extending operating position has a leading edgeforming a convex curve which inclines rearwards as it descends to a tip.The fin has a rear or trailing surface that rises again to the lowersurface of the board. The fins are designed to cut through the waterwith low drag and offer high resistance in a lateral direction to limittransverse movement of the surfboard through the water. This enables asurfboard to maintain its forward trajectory along a wave while alsoallowing a surfer to turn the surfboard on the wave. The lateralresistance is necessary for the surfer to perform directional changes ona wave that are smooth, arcuate and controlled.

Applicant is also aware of some developments in the arrangement of finson a surfboard. FIG. 1 illustrates an early form of surfboard having asingle fin centrally positioned on the board towards the rear thereof.The manoeuvrability of the surfboard illustrated in FIG. 1, and inparticular its ability to turn on a wave, is quite limited. A surferriding a ‘single fin’ surfboard will have good straight line stabilityand good “projection”, meaning that the surfer can move at speed “downthe line”. They can then pick a point on the wave ahead of them and byapplying a strong turning force perform a smooth arcing turn of wideradius and arrive accurately and predictably at that point. The surfermay subsequently wish to perform a strong ‘cutback’ turn of sharperradius without losing speed. While a surfer having considerable skilland experience can turn tightly, given the right wave conditions, asingle fin surfboard is inherently unsuited to making tight turns.

FIG. 2 illustrates a later form of prior art surfboard that becamepublicly available after the surfboard shown in FIG. 1 and is known as a“twin fin” board. It has two laterally spaced side fins on either sideof a midline of the board. It does not have a centrally positioned finlike the board in FIG. 1. The “twin fin” was developed in competitionsurfing in response to a lack of an ability to make tight turns, i.e., a“stiffness” of the single fin. Substantial improvements in turningperformance were achieved by replacing the single fin with two finsplaced further toward the front and out toward the sides or “rails” ofthe surfboard. Conveniently, the surfer could perform a series of tightradius turns, with the fins alternately forming the pivot points forleft and right turns. The twin fin is known to be a “loose”, freeturning surfboard. However, this improvement in turning capability cameat the cost of the “projection” possessed by the single fin surfboard.

FIG. 3 illustrates a later form of prior art surfboard that becamepublicly available after the surfboard shown in FIG. 2. The surfboard inFIG. 3 has a tri-fin arrangement towards a rear of the board and isknown as a thruster. The board has two side fins on either side of acentrally positioned trailer fin. The thruster fin arrangement shown inFIG. 3 is a hybrid or combination of the surfboards in FIGS. 1 and 2 andprovides a greater ability to turn on a wave, and in particular, turnsharply, than the surfboard illustrated in FIG. 1. This board thusenables a surfer to perform more intricate manoeuvres when riding awave. This was seen as a breakthrough because the ability to manoeuvreand turn sharply on a wave is important in competition surfing. The“thruster” was developed in an attempt to capture the “projection” ofthe single fin, while retaining the advantageous turning ability of thetwin fin. The thruster surfboard, which is a combination of the singlefin and twin fin designs, has been extremely successful, and the largemajority of commercially available surfboards use this design. However,the fact remains that this design remains a compromise between the twinfin and the thruster.

FIG. 4 illustrates an even later form of prior art surfboard that becamepublicly available after the surfboard shown in FIG. 3. The board inFIG. 4 which is known as a “quad” has a pair of side fins on one side ofthe midline of the board and another pair on the other side thereof. Thetwo fins within each pair are closely spaced both laterally andlongitudinally relative to each other. As shown in the drawing, theleading fin in each pair is positioned laterally outward of the trailingfin in that pair. The quad has recently seen a resurgence as surferscontinue to seek the elusive optimum combination of turning ability andprojection.

As far as the Applicant is aware, there have been no significant furtherdevelopments in fin design or fin placement implemented on commerciallyavailable surfboards since 1985. Since then, manufacturers haveenergetically continued their efforts to improve the performance ofleisure and competition surfboards, but the changes they have proposedessentially involve trying different combinations of known designs.Consequently, many commercially available surfboards have five finboxes, allowing the surfer to experiment with different finconfigurations, like those described above with reference to FIGS. 1 to4. In summary, recent innovations in the manufacture of surfboardsinvolve re-arranging and tweaking the known combinations that arediscussed above.

The reference to prior art in the background above is not and should notbe taken as an acknowledgement or any form of suggestion that thereferenced prior art forms part of the common general knowledge inAustralia or in any other country.

SUMMARY OF THE INVENTION

While the development of fin designs has provided surfboards with somemanoeuvrability and an ability to change direction, Applicant recognizesthat it would be beneficial if the manoeuvrability of surfboards couldbe further increased.

Applicant recognizes that prior art fin designs are unable toautomatically adjust (i.e., auto-adjust) the angle of the fin to a lineof travel through the water because the fins are rigidly fixed to theboard. Applicant recognizes that it would be beneficial if a devicecould be devised that at least ameliorated this limitation.

According to one aspect of the invention there is provided a watercraftmanoeuvring device for mounting on a watercraft operated by a user, thewatercraft manoeuvring device comprising:

an elongate member having a mounting end and a fin end that is opposedto said mounting end, wherein the elongate member is capable of flexingwhen the device is travelling through water;

a mounting formation on or at the mounting end of the elongate memberfor mounting on the watercraft; and

a fin at the fin end of the elongate member having a bearing surface forinteracting with water through which the fin travels.

The device helps the user to manoeuvre a watercraft as it travels acrossa surface of water.

The elongate member may have a length of 1 mm to 1200 mm. In some forms,the elongate member may have a length in the range of 10 mm to 500 mm.Optionally, the elongate member may have a length in the range of 20 mmto 250 mm, e.g., 30 mm to 150 mm.

The length of the elongate member can be varied to produce a devicehaving different operational or ride characteristics.

For example, a watercraft manoeuvring device having a relatively shorterelongate member may be replaced with a device having a relatively longerelongate member.

Further, a watercraft manoeuvring device having a relatively stifferelongate member may be replaced with a device having an elongate memberwith a greater whip or flexibility.

The fin on the elongate member may be resiliently flexible and may becapable of an angular deflection of up to 30 degrees from its restingposition, e.g., 15 to 30 degrees. This angular deflection can bereferred to as a sway angle.

The length of the elongate member influences the length of an arcthrough which the fin can be displaced when the elongate member flexesin use.

The elongate member may have a maximum cross-sectional dimensionalextent that does not exceed 35 mm. Optionally, the elongate member mayhave a maximum cross-sectional dimensional extent of 10 to 30 mm, e.g.,15 to 25 mm.

The elongate member may have a cross-sectional configuration that curvesaround its full circumferential extent.

The elongate member may have a circular cross-sectional configurationand the elongate member may have a cross-sectional diameter in the rangeof 15 to 30 mm.

Instead, the elongate member may have an ovoid or ellipticalcross-sectional configuration. Yet further instead, the elongate membermay have a rectangular or H-shaped cross section along its length.

The elongate member may be solid. Alternatively, the elongate member maybe hollow along at least part of its length.

The elongate member, the mounting formation and the fin may beintegrally formed of a resiliently flexible material. Optionally, theymay be formed of a polymeric material, e.g., including reinforcingmaterials. The reinforcing materials may include glass fibre or carbonfibre and may be in the form of a mat.

The elongate member may have a degree of flexibility or whip that issimilar to that of a fishing rod.

The mounting formation may have a leading end at a forward end of thedevice and a rear end at a rearmost point of attachment of the device tothe watercraft.

Thus, the mounting formation terminates at the rearmost point at whichit is fixed to the watercraft. Correspondingly, the elongate membercommences or starts after this point, namely after the rearmost point ofattachment to the watercraft, and this provides a reference formeasuring the length of the elongate member.

The mounting formation may be detachably mountable to the watercraft.

The mounting formation may include a projection for receiving in acomplementary socket in the watercraft to detachably mount it to thewatercraft.

Conveniently, the complementary socket or recess may be formed by a finbox which is permanently mounted in the board.

The mounting formation may have a low profile to streamline water flowover the formation and to minimize resistance by the mounting formation.

Further, instead of being removable, the mounting formation at themounting end of the elongate member may be permanently mounted to thebody of the watercraft.

For example, the mounting formation at the mounting end of the elongatemember may be glassed, optionally with fibre, into the body of theboard, e.g., in the same way a fin can be glassed into the body of aboard.

The elongate member serves to rearwardly cantilever the fin on thedevice into a dynamic position. The elongate member has a freedom andability to flex that enables the fin to adjust its position, e.g., angleof attack, through the water and relative to water flow. This may bereferred to as a live sprung fin. Without being bound by theory,Applicant believes this streamlines water flow over the fin and allowsfor laminar rather than turbulent flow over the fin. Applicant alsoanticipates that it may release energy which is directed into forwardmomentum.

The fin may comprise a fin base and a fin tip and a convex leading edgeextending from the fin base to the fin tip and a concave trailing edgeextending from the fin tip back down to the fin base, and the fin may befixed to the fin end of the elongate member such that the fin moves withthe elongate member.

Instead of being integrally formed with the elongate member, the fin mayoptionally be releasably attached to the fin end of the elongate member.This feature creates the possibility for one fin to be substituted foranother on the same manoeuvring device. For example, fins of variousshapes and surface areas and thereby different ride characteristics maybe interchangeably attached to the fin end of the elongate member.

According to another aspect of the invention there is provided awatercraft for travelling across the surface of water, the watercraftcomprising:

an elongate body having an operatively upper surface for a user and anoperatively lower surface for facing down into water, and

a watercraft manoeuvring device mounted on the elongate body comprising,an elongate member having a mounting end and a fin end that is opposedto said mounting end, the elongate member being capable of flexing whenthe device is travelling through water, a mounting formation on themounting end of the elongate member mounted on the elongate body, and afin on the fin end of the elongate member, e.g., having bearing surfacefor interacting with water through which the fin travels.

The elongate member may be resiliently flexible for flexing whentravelling through water.

The watercraft manoeuvring device may be mounted on the operativelylower surface of the elongate body.

The elongate member may extend substantially parallel to the operativelylower surface of the elongate body.

Further, the elongate member may be vertically positioned at a height ofnot more than 100 mm beneath the operatively lower surface.

Optionally, the elongate member may be arranged vertically positioned ata height of not more than 50 mm beneath the operatively lower surface,e.g., not more than 35 mm beneath the operatively lower surface.

The mounting formation may be positioned forward of the fin of thewatercraft manoeuvring device on the elongate body.

The elongate body may have a front end and a rear end, and thewatercraft manoeuvring device may be mounted towards the rear end of thebody.

Further, the fin of the watercraft manoeuvring device may be positionedforward of the tail of the elongate body.

The elongate body may have a center line extending along the length ofthe body, and the watercraft manoeuvring device may be mountedsubstantially along the center line of the elongate body.

The watercraft may further include at least one fixed fin directly andrigidly mounted on the operatively lower surface of the elongate body.

Optionally, the watercraft may include two said fixed fins mountedrespectively on left and rights sides of the center line of the board.

The rigid fins on the left and right sides of the body may be laterallyaligned with each other and may be positioned rearward of the fin of thewater manoeuvring device.

The mounting formation may be detachably mounted to the elongate body toenable the device to be detached from the board and replaced withanother device.

The elongate body may have a plurality of fin boxes in the operativelylower surface thereof, and each of the fin boxes may be configured toreleasably clamp the mounting formation of the water craft manoeuvringdevice to the elongate body.

Providing a plurality of fin boxes positioned on the elongate bodyprovides a user with a plurality of different options for positioningthe elongate member in different positions on the device. For example,the several options enable the user to vary the position of the deviceon the elongate body. It also enables the user to select devices havingdifferent lengths of elongate member without significantly changing thelongitudinal position of the fin of the device.

Alternatively, the watercraft manoeuvring device may be mounted on anoperatively upper surface of the elongate body.

Further alternatively, the watercraft manoeuvring device may be mountedon the rear end of the elongate body.

The watercraft manoeuvring device of the watercraft may include any oneor more of the optional or preferred features of the watercraftmanoeuvring device defined in any preceding aspect of the invention.

Optionally, the watercraft may be a surfboard. Instead, the watercraftmay be a windsurfer.

According to yet another aspect of the invention there is provided asurfboard comprising:

an elongate board having a nose and a tail and two rails extendingbetween the nose and the tail, an operatively upper surface forming adeck on which a user stands and an operatively lower surface for facingdown into water; and

a watercraft manoeuvring device mounted on the elongate boardcomprising, an elongate member having a mounting end and a fin end thatis opposed to said mounting end, wherein the elongate member is capableof flexing when the board is travelling through water, a mountingformation on the mounting end of the elongate member mounted on thelower surface, and a fin on the fin end of the elongate member.

The elongate member may have a length of 1 mm to 500 mm. Optionally, theelongate member may have a length of 30 to 150 mm.

The elongate member may extend substantially parallel to the operativelylower surface of the board.

The elongate member may be positioned a vertical distance, e.g., aheight of not more than 100 mm beneath the operatively lower surface.Optionally, the elongate member may be vertically positioned at a heightof not more than 50 mm beneath the operatively lower surface

The elongate member may have a cross-sectional configuration that curvesaround its full circumferential extent, and the elongate member may havea maximum diameter of 30 mm.

Optionally, the elongate member may have a maximum diameter in the rangeof 15 to 30 mm, e.g., 15 to 25 mm.

Optionally, the elongate member may have a circular or ovoid orelliptical cross-sectional configuration.

The watercraft manoeuvring device may be integrally formed from apolymeric material, and the mounting formation may be detachably mountedon the board whereby to enable the device to be detached from the boardand replaced with another device.

The watercraft manoeuvring device may be mounted on a center line of theboard, and the board may further include left and right fixed fins onleft and right sides of the center line that are directly mounted to theboard (and cannot alter their angle of travel relative to the board).

The watercraft manoeuvring device and the left and right fixed fins maybe mounted in suitable positions on the board to enable the longitudinaland lateral positions of the fin of the device and the fixed finscollectively to resemble a tri fin thruster configuration.

That is, the fins are mounted in basically the same position as the finson a thruster. However, the central fin forms part of a manoeuvringdevice that has an elongate member which can flex and consequently thefin can alter its line of travel through the water.

The one and other fixed fins may be bilaterally symmetrical on the body,e.g., they may be laterally aligned on the body and may be spaced anequal distance from the midline.

The watercraft manoeuvring device on the surfboard may include any oneor more of the optional or preferred features of the watercraftmanoeuvring device defined in any preceding aspect of the invention.

The invention extends to a method of modifying a watercraft, e.g., asurfboard having an elongate board with at least one removable fin on anunderside of the board, the method including:

removing a fin from an underside of the board and replacing it with awatercraft manoeuvring device as defined in any one of the precedingaspects of the invention.

The removable central fin may be removably mounted on the board by meansof a clamp which releasably clamps the fin into a fin box mounted in theboard.

Removing the central fin may include releasing the clamp and withdrawingthe fin, e.g., a central fin, from the fin box.

Replacing the central fin with a surfboard manoeuvring device mayinclude inserting the surfboard manoeuvring device into the fin box andclamping it to the fin box.

The watercraft manoeuvring device of the surfboard may include any oneor more of the optional or preferred features of the watercraftmanoeuvring device defined in any preceding aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A watercraft manoeuvring device and a surface watercraft that is asurfboard including the manoeuvring device in accordance the inventionmay manifest itself in a variety of forms. It will be convenient tohereinafter describe in detail several embodiments of the invention withreference to the accompanying diagrammatic drawings. The purpose ofproviding this detailed description is to instruct persons having aninterest in the subject matter of the invention how to carry theinvention into practical effect. However, it is to be clearly understoodthat the specific nature of this detailed description does not supersedethe generality of the preceding summary section.

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the disclosure andtogether with the detailed description herein, serve to explain theprinciples of the disclosure. It is emphasized that, in accordance withthe standard practice in the industry, various features are not drawn toscale. In fact, the dimensions of the various features may bearbitrarily increased or reduced for clarity of discussion. The drawingsare only for purposes of illustrating preferred embodiments and are notto be construed as limiting the disclosure.

FIG. 1 is a lower perspective view of a surfboard in accordance with theprior art having a single tail fin centrally positioned on the board, inaccordance with an aspect of the present disclosure;

FIG. 2 is a lower perspective view of another surfboard in accordancewith the prior art having two laterally spaced side fins mounted on theboard, in accordance with an aspect of the present disclosure;

FIG. 3 is a lower perspective view of yet another surfboard inaccordance with the prior art having three tail fins mounted on theboard, in accordance with an aspect of the present disclosure;

FIG. 4 is a lower perspective view of yet another surfboard inaccordance with the prior art having two pairs of tail fins, one pairbeing mounted on each side of the board, in accordance with an aspect ofthe present disclosure;

FIG. 5 is a lower perspective view of a watercraft manoeuvring devicethat is a surfboard manoeuvring device in accordance with one embodimentof the invention;

FIG. 6 is a bottom plan view of the surfboard manoeuvring device of FIG.5, in accordance with an aspect of the present disclosure;

FIG. 7 is a front view of the surfboard manoeuvring device of FIG. 5mounted on a surfboard, in accordance with an aspect of the presentdisclosure;

FIG. 8 is a side view of the surfboard manoeuvring device of FIG. 5mounted on a surfboard, in accordance with an aspect of the presentdisclosure;

FIG. 9 is a lower perspective view of a surfboard fitted with thesurfboard manoeuvring device of FIG. 5, in accordance with an aspect ofthe present disclosure;

FIGS. 10 and 11 illustrate different embodiments of surfboardmanoeuvring devices mounted on a surfboard like that shown in FIG. 9, inaccordance with an aspect of the present disclosure;

FIG. 12 is a schematic side view of a surfboard having a surfboardmanoeuvring device in accordance with another embodiment of theinvention mounted thereon, in accordance with an aspect of the presentdisclosure;

FIG. 13 is a schematic side view of a surfboard having a surfboardmanoeuvring device in accordance with yet another embodiment of theinvention mounted thereon, in accordance with an aspect of the presentdisclosure;

FIGS. 14 and 15 are schematic side and plan views of a surfboard havinga surfboard manoeuvring device in accordance with yet another embodimentof the invention mounted thereon, in accordance with an aspect of thepresent disclosure;

FIG. 16 is a schematic drawing of the watercraft manoeuvring device inaccordance with an embodiment of the invention mounted on a surfacewatercraft that is a windsurfer, in accordance with an aspect of thepresent disclosure; and

FIG. 17 is a schematic drawing of a surfboard in accordance with anotherembodiment of the invention, in accordance with an aspect of the presentdisclosure.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

FIGS. 1 to 4 illustrate surfboards that are known in the prior art. Thefin arrangements illustrated in FIGS. 1 to 4 have been described abovein the background section of the specification. As these prior artsurfboards do not form part of the invention claimed in thisapplication, they will not be described further in this detaileddescription.

FIGS. 5 to 8 illustrate a watercraft manoeuvring device that is asurfboard manoeuvring device for mounting on an operatively lowersurface or bottom of a body or hull of a surfboard. In the drawings,reference numeral 10 refers generally to the surfboard manoeuvringdevice.

The surfboard manoeuvring device 10 comprises broadly an elongate memberor boom 12 including a mounting end 14 and a fin end 18. The mountingend 14 has a mounting formation 16 for detachably mounting the device 10to the lower surface of a watercraft, and an opposed fin end 18. Thedevice 10 further includes a fin 20 on the fin end 18 of the elongatemember 12 for interacting with the water through which the surfboardtravels.

The mounting formation 16 extends from its forward attachment to theboard to its rear point of attachment to the board. The elongate member12 starts at the rearmost point at which the mounting formation is fixedto the board. This provides a reference point for measuring the lengthof the elongate member 12. This is also consistent with the concept thatthe elongate member 12 is free to flex relative to the board and is notfixed or held to the board like a mast.

The elongate member 12 is formed of a resilient material having somestiffness but which can bend along its length when it is subjected toforces from the water through which it travels. In one example form, theelongate member 12 has a length of 10 to 300 mm and a substantiallycircular, an elliptical or an ovoid cross-sectional shape that isconstant along its length. The rounded cross-sectional configuration ofthe elongate member 12 helps to streamline the member 12 and reducedrag. The elongate member or boom 12 may be rod-like and be formed froma resilient material that can flex along its length and then return toits original form repeatedly without suffering any loss of stiffness inthe material. The desired flexural performance of the elongate member 12is achieved by appropriate selection of material, thickness, and length,and also by selecting a suitable profile for the member.

Conveniently, the surfboard manoeuvring device 10 may be integrallyformed from a polymeric material, optionally with some fibre andcomposite material that provides a suitable strength and that alsoconfers a desired flexibility. The existence of high performing plasticssuch as polycarbonate, polyamide (NYLON), acetyl or acetal resins andthermo-setting resins such as epoxy and polyester, and also carbonfibre, enables the elongate member 12 to be manufactured with a desiredstiffness while still being resilient. It also enables the entiremanoeuvring device 10 to be integrally formed in one unitary piece byCNC machining, injection moulding or by hand lay up. Optionally, thesurfboard manoeuvring device can also be made of a sustainable materialsuch as bamboo.

FIG. 9 illustrates a surfboard indicated generally by the referencenumeral 30 comprising an elongate body or board 32 having an operativelyupper surface or deck 34 and an operatively lower surface or bottom 36extending between a front end or nose 37 and an opposed rear end or tail38. The board also has rails extending down its sides between the nose37 and the tail 38.

The surfboard 30 has a fin arrangement towards the rear end 38 of thebody 32 for helping a surfer to manoeuvre the surfboard on a wave. Inthe illustrated embodiment, the fin arrangement comprises twoconventional surfboard fins or rigid side fins 42, 44, one on eitherside of the body 32, and a surfboard manoeuvring device 10 like that inFIGS. 5 to 8 which is mounted substantially centrally between the twoside fins 42, 44 a small distance rearward of the side fins 42, 44.

In the illustrated embodiment, the mounting formation 16 at the mountingend 14 of the resilient member 12 comprises a couple of mountingprotrusions or projections 52, 54 that project away from the mountingend 14 of the member 12 that are tightly received within complementarysockets or apertures 56 within a fin box on the body 32 of the board 30.The fin box is a commercially available product is built into thesurfboard by the board manufacturers during the manufacture thereof.

The projections 52, 54 are clamped to the body 32 in the fin box inaccordance with known techniques. In the illustrated embodiment, thesurfboard manoeuvring device 10 is releasably clamped, to the body 32which is very useful. It enables the surfboard manoeuvring device 10 tobe quickly and easily detached and removed from the surfboard 30. It canthen be replaced with another surfboard manoeuvring device 10, e.g., ofa different size and having different operational properties.

FIG. 17 illustrates a surfboard that is a variation on the surfboarddescribed above with reference to FIG. 9. The same reference numeralswill be used to refer to the same components unless otherwise indicated.

In FIG. 17, the mounting formation 16 is positioned forward on the board32 relative to that in FIG. 9. This has a follow on effect that the fin20 of the device 10 is positioned in substantially the same longitudinalposition as a central fin in a tri-fin thruster arrangement. Further,the elongate member travels close to the bottom of the board parallel tothe surface of the board and thus the fin of the device is in a verysimilar vertical position to the central fin of a prior art thruster finarrangement. Thus, this arrangement mimics the tri fin thruster and theboard visually resembles a regular surfboard with a widely used tri-finthruster. The surfboard in FIG. 17 in a broad sense facilitates the samesurfing manoeuvres as those carried out with a thruster. However, itperforms better than the prior art thruster for the reasons described inthis specification.

If the position of the fin 20 of the device 10 along the length of theboard 32 is to be set as described immediately above, then one way toaccommodate different lengths of elongate member 12 is to move the axialposition of the mounting formation 16 along the board. If, for example,a device 10 with longer elongate member 12 is desired to be used on theboard of FIG. 17, then the mounting formation 16 can be moved forward onthe board 32 to keep the fin 20 of the device 10 in substantially thesame longitudinal position. A range of fin boxes arranged in differentaxial positions on the bottom of the board facilitates this optionality.

In use, the surfboard manoeuvring device 10 is mounted on a surfboard 30in the manner shown in FIG. 7. That is, the surfboard manoeuvring device10 is centrally mounted on the operatively lower surface 36 of the body32 towards the rear end 38 thereof. The surfboard manoeuvring device 10is mounted on the body 32 by inserting the mounting formations 52, 54into the complementary sockets 56 in the board 32 and clamping themounting formations thereto.

The surfboard manoeuvring device 10 provides the user of the surfboard30 or surfer with an enhanced ability to manoeuvre the surfboard 30. Inparticular, flexing of the elongate member 12 of the device increasesthe power of the surfboard 30 as it travels through the water. It alsoenables the surfer to control their movements across the water surfacemore precisely.

FIGS. 10 and 11 illustrate surfboard manoeuvring devices in accordancewith further embodiments of the disclosure. In FIGS. 10 and 11, unlessotherwise indicated, the same reference numerals will be used to referto the components as in FIGS. 5 to 8. Further, the following descriptionwill focus on the main differences between the embodiments in FIGS. 10and 11 and the embodiments in the earlier embodiment shown in FIGS. 5 to8.

In FIG. 10, the device 10 has a shorter elongate member 12 than theelongate member of the device 10 in FIGS. 5 to 8. As shown in thedrawing, the device 10 terminates short of the rear end 38 of thesurfboard 32. The effect of the shorter member 12 on the operation ofthe surfboard will be to impart good projection and a stiffer feel whenturning the surfboard.

In FIG. 11, the device 10 has a longer elongate member than the elongatemember 12 on the device 10 in FIGS. 5 to 8. In particular in FIG. 11,the fin of the device 10 projects out beyond the rear end 38 of theboard 32. The effect of this change on the operation of the board willdepend on the stiffness of the elongate member. A longer but relativelystiffer elongate member 12 will impart good directional projection to ashort surfboard fitted with the device 10. A relatively more flexibleelongate member 12 will impart a greater turning ability to thesurfboard.

FIG. 12 is a schematic side view of a surfboard fitted with a surfboardmanoeuvring device in in accordance with another embodiment of theinvention. Again, the same reference numerals will be used to refer tothe same components and the following description will focus on thedifference between this embodiment and the earlier embodiments.

In the FIG. 12 embodiment, the surf craft manoeuvring device 10 ismounted to an upper surface or deck 34 of the body 32 or board of thesurfboard 30 (instead of the lower surface 36). The device 10 may have amounting formation 16 mounted in a fin box similar to that used on thelower surface 36 of the board 32.

FIG. 13 is a schematic side view of a surfboard fitted with a surfboardmanoeuvring device in accordance with yet another embodiment of theinvention. Once again, the same reference numerals will be used to referto the same components unless otherwise indicated and the descriptionwill focus on the differences between this embodiment and the earlierembodiments.

In FIG. 13, the surf craft manoeuvring device 10 is mounted to the rearend 38 of the board 32 of the surfboard 30. The board 32 has a fin boxwithin which a mounting formation 16 on the device 10 is received.

FIGS. 14 and 15 are schematic side and plan views of a surfboard fittedwith a surfboard manoeuvring device in accordance with yet anotherembodiment. Once again, the same reference numerals will be used torefer to the same components unless otherwise indicated and thefollowing description will focus on the difference between thisembodiment and the earlier embodiments.

In FIGS. 14 and 15, the device is mounted to an operatively lowersurface or bottom 36 of the surfboard 30 towards the tail 38 thereof.The device 10 has a fin 200 having bearing surfaces extending in asubstantially horizontal direction whereas the fin 20 of the earlierembodiments has bearing surfaces extending in a vertical direction. Thebearing surfaces extend laterally away from both sides of the elongatemember 32 or flex boom.

The elongate member 12 turns down towards the fin end 18 thattransitions into the fin 20. This positions the fin 20 at a suitabledistance or vertical height beneath a surface of water to enable it toapply a force to water passing over an upper surface of the fin 200without leaving the water. The design of the fin 200 allows the user topropel the surfboard 30 forward by a rocking up and down leg drivingmotion known in surfing as ‘leg pumping’.

FIG. 16 shows the watercraft manoeuvring device mounted to a windsurfer.Once again, the same reference numerals will be used to refer to thesame components unless otherwise indicated and the following descriptionwill focus on the difference between this embodiment and the earlierembodiments.

The windsurfer is referred to generally by the numeral 60 and comprisesa windsurfer body 62 having an operatively upper surface or deck and anoperatively lower or water facing surface. The watercraft manoeuvringdevice 10 is mounted to the windsurfer 60 towards the rear of the body62 in a similar manner to the mounting to a surfboard.

In use, the watercraft manoeuvring device 10 functions in a similarmanner to the device used on the surfboard. Its main advantage is itsability to self-adjust the angle of the fin to the water flow. The hullof a wind surfer frequently leaves the water during use. It takes askilled user to return the hull to the water at exactly the right angle.The device of this invention enables the fin of the device to autoadjust on its return to the water.

The prior art fins, such as those shown in FIGS. 1 to 4, can beconstructed to have two foundation axes. The axes comprise a verticalmast axis extending perpendicularly away from the board and a horizontalboom axis extending rearward from the vertical mast axis. The mast andthe boom are bearing surfaces that bear against the water through whichthe board is passing. Further, prior art fins have a base or foot thatis fixed directly to the board and cannot move relative thereto in use.The Applicant has found no exceptions to this mode of fin constructionin the prior art.

In the current application, the fin of the watercraft manoeuvring deviceis axially separated from the mounting formation which mounts it to thesurfboard. Thus, the device illustrated above with reference to thedrawings differs from the prior art fins in that it has no vertical mastfast with the board and extending away therefrom that acts as a bearingsurface.

The illustrated embodiments of fins and devices in accordance with thecurrent disclosure have no vertical mast. Instead, the devices have anelongate member in the form of a stanchion or knuckle member attached tothe board that presents no bearing surface. Rather, the stanchion has afin having a bearing surface at a remote end thereof which moves withthe stanchion and is not directly fixed to the board.

The watercraft manoeuvring device, by means of the elongate member orstanchion, enables the fin to auto adjust its angle through the water toan angle of least resistance through the water. The elongate member canflex in response to hydrodynamic water forces that are applied theretoand can self-adjust the angle of the fin relative to the surfboard body.The change in angle of the fin can occurs without bending or distortingthe fin which itself would alter the performance of the fin.

The fin has a bearing surface for interacting with water and theelongate member is capable of flexing when the fin is subjected tohydrodynamic water forces when travelling through water. This feature ofself-adjusting the angle of the fin enables the surfboard to turnsmoothly and also avoids a stalled fin situation because it provides formore streamlined flow over the surface of the fin. There is lessturbulence and consequently less drag to cause the surfboard to stall.

Applicant is aware of high performing polymeric and composite materialsthat make it possible to manufacture an elongate member that is stiffbut also flexes resiliently as the device travels through the water. Theflexing and resilience also stores, and then releases spring energywhich is directed into forward momentum.

An advantage of the surfboard described above with reference to FIGS. 5to 17 is that it provides a surfer with increased manoeuvrability andpower when surfing a wave. It therefore provides a more exciting surfingexperience than a prior art surfboard having traditional fixed fins.Applicant also anticipates that a surfer using a board fitted with thedevice would be able to use known ‘leg pumping’ techniques to drive theboard forward through the water.

The device can be used in combination with two side fins so that theytogether resemble a prior art thruster fin arrangement on a surfboard.That is, the three fins (including the fin of the manoeuvring device)are positioned in broadly the same relative position to each other andthe board as with the prior art thruster. The mounting formation for thedevice 10 will be positioned more forward on the board than the mountingformation of a central fin of a thruster fin arrangement. This enablesthe actual fin 20 on the device 10 to be positioned in the same axialposition as it would occupy with a thruster fin arrangement.Additionally, the elongate member extends parallel to the surface of theboard so that the height of the fin on the device is at broadly the sameheight as the central fin of the thruster arrangement.

Without being bound by theory, Applicant believes that the devicedescribed above with reference to the drawings mimics the propulsiveproperties of fluke fins of whales and dolphins in nature. Finally,Applicant believes that the current disclosure opens the door to a freshchapter of development in surfboard design and performance.

It is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrativeonly and not limiting. All such modifications and variations thereto, aswould be apparent to persons skilled in the art, are deemed to fallwithin the broad scope and ambit of the invention as is set forthherein. Changes in detail or structure may be made without departingfrom the basic elements of the invention as defined in the followingclaims.

What is claimed is:
 1. A watercraft manoeuvring device for mounting on awatercraft, the watercraft manoeuvring device comprising: an elongatemember having a mounting end and a fin end that is opposed to saidmounting end, wherein the elongate member is capable of flexing; amounting formation on the mounting end of the elongate member formounting on the watercraft; and a fin at the fin end of the elongatemember having a bearing surface for interacting with water through whichthe fin travels.
 2. The watercraft manoeuvring device of claim 1,wherein the elongate member has a length of 1 mm to 1200 mm.
 3. Thewatercraft manoeuvring device of claim 1, wherein the fin on theelongate member is capable of an angular deflection of 15 to 30 degreesfrom its resting position due to flexing of the elongate member duringuse.
 4. The watercraft manoeuvring device of claim 1, wherein theelongate member has a cross-sectional configuration that curves aroundits full circumferential extent, and the elongate member has a maximumcross-sectional dimensional extent that does not exceed 30 mm.
 5. Awatercraft manoeuvring device of claim 1, wherein the elongate member,the mounting formation and the fin are integrally formed of aresiliently flexible material, and the mounting formation is detachablymountable to the watercraft.
 6. The watercraft manoeuvring device ofclaim 5, wherein the mounting formation has a leading end at a forwardend of the device and a rear end at a rearmost point of attachment tothe watercraft, and the mounting formation includes a mountingprojection for inserting in a complementary socket in the watercraft todetachably mount the device to the watercraft.
 7. A watercraft fortravelling across the surface of water, the watercraft comprising: anelongate body having an operatively upper surface for a user and anoperatively lower surface for facing down into water, and a watercraftmanoeuvring device mounted on the elongate body, comprising an elongatemember having a mounting end and a fin end that is opposed to saidmounting end, the elongate member being capable of flexing when thedevice is travelling through water, a mounting formation on the mountingend of the elongate member mounted on the elongate body, and a fin onthe fin end of the elongate member.
 8. The watercraft for travellingacross the surface of water of claim 7, wherein the elongate body has afront end and a rear end, and the watercraft manoeuvring device ismounted on the operatively lower surface of the elongate body towardsthe rear end thereof.
 9. The watercraft for travelling across thesurface of water of claim 7, wherein the elongate member extendssubstantially parallel to the operatively lower surface of the elongatebody, and the elongate member is positioned a vertical distance of notmore than 100 mm beneath the operatively lower surface of the body. 10.The watercraft for travelling across the surface of water of claim 7,wherein the elongate body has a center line extending along a length ofthe elongate body and the watercraft manoeuvring device is mounted onthe center line of the elongate body.
 11. The watercraft for travellingacross the surface of water of claim 10, wherein the watercraft is asurfboard and further includes at least one fixed fin rigidly mounted onthe operatively lower surface of the elongate body.
 12. The watercraftfor travelling across the surface of water of claim 11, including twosaid fixed fins mounted respectively on left and rights sides of thecenter line of the board.
 13. The watercraft for travelling across thesurface of water of claim 12, wherein the fixed fins on the left andright sides of the body are laterally aligned with each other and thefixed fins are positioned forward of the fin of the water manoeuvringdevice.
 14. The watercraft for travelling across the surface of water ofclaim 7, wherein the mounting formation is detachably mounted to theelongate body, and the elongate body has a plurality of fin boxes in theoperatively lower surface, and each fin box is configured to releasablyclamp the mounting formation of the water craft manoeuvring device tothe elongate body.
 15. A surfboard comprising: an elongate board havinga nose and a tail and two rails extending between the nose and the tail,an operatively upper surface forming a deck on which a user stands andan operatively lower surface facing down; and a watercraft manoeuvringdevice mounted on the elongate board comprising, an elongate memberhaving a mounting end and a fin end that is opposed to said mountingend, wherein the elongate member is capable of flexing when the board istravelling through water, a mounting formation on the mounting end ofthe elongate member that is mounted on the lower surface, and a fin onthe fin end of the elongate member.
 16. The surfboard of claim 15,wherein the elongate member has a length of 1 mm to 500 mm, and theelongate member extends substantially parallel to the operatively lowersurface of the board.
 17. The surfboard of claim 16, wherein theelongate member has a length of 30 to 150 mm, and the elongate member ispositioned a vertical distance of not more than 50 mm beneath theoperatively lower surface.
 18. The surfboard of claim 15, wherein theelongate member has a cross-sectional configuration that curves aroundits full circumferential extent, and the elongate member has a maximumdiameter of 15 to 30 mm.
 19. The surfboard of claim 15, wherein thewatercraft manoeuvring device is integrally formed from a polymericmaterial, and wherein the mounting formation is detachably mounted onthe board whereby to enable the device to be detached from the board andreplaced with another device.
 20. The surfboard of claim 15, wherein thewatercraft manoeuvring device is mounted on a center line of the board,and the board further includes left and right fixed fins on left andright sides of the center line that are directly mounted to the board,and wherein the watercraft manoeuvring device and the left and rightfixed fins are mounted on the board such that the longitudinal andlateral positions of the fin of the device and the fixed fins resemble atri fin thruster configuration.